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SEVEN DECADES OF EAST AFRICAN
MIOCENE ANTHROPOID STUDIES
Russell H. Tuttle*
1. INTRODUCTION
African Miocene anthropoid studies followed a full century after pioneer work in Europe
and South Asia. Indeed, Eurasian fossil apes were collected decades before the Darwinian
revolution. Pliopithecus is the first fossil primate known to Western science. Edouard
Lartet discovered the type mandible near Sansan, France, in 1834; and, the Eppelsheim
femur, which resembles Slovakian femora of Pliopithecus, was found in Germany in 1820
(Piveteau, 1957; Pohlig, 1895; McHenry and Corruccini, 1976). In 1856, Lartet introduced Dryopithecus fontani from southwestern France.
South Asian Miocene anthropoids came to the attention of the wider scientific community when Pilgrim published findings on them in the 1910s. Vertebrate faunas had been
collected from the Siwaliks by Falconer and Cautley (1830–1850) for the British Museum
and by Richard Lydekker (1876–1886) and Guy Pilgrim (1900–1930) for the Geological
Survey of India Museum in Calcutta. Barnum Brown collected for the American Museum
of Natural History in 1922–23 and G. Edward Lewis collected for the Yale Peabody Museum in 1931–33. In 1935, DeTerra collected specimens with the Yale–Cambridge India
Expedition (Khatri, 1975).
The earliest studies of African Miocene anthropoid primates were focused on western
Kenyan specimens. In 1933, A. Tindell Hopwood of the British Museum diagnosed a
dozen dental and gnathic specimens that had been collected between 1926 and 1931 in the
Koru area of Kenya. He named two “gibbon-like” mandibular fragments Limnopithecus
legetet and dubbed a maxillary fragment and a deciduous molar Xenopithecus koruensis.
Hopwood considered that both species represented extinct lineages. He named the remainder of the specimens Proconsul africanus and concluded that they were related to
Dryopithecus and were ancestral to Pan troglodytes. Thus began the search-for-the-superlative period, in which researchers strove to link novel specimens directly to extant
hominoid species.
* Russell H. Tuttle, Department of Anthropology, The University of Chicago, 1126 E. 59th Street, Chicago, IL
60637-1614, USA.
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R. H. TUTTLE
2. COLLECTION AND INTERPRETATION: 1931–1959
In 1931 and 1932, Louis Leakey, Donald MacInnes, and other members of the third East
African Archaeological Expedition discovered Miocene anthropoid fossils on Rusinga Island, at the mouth of the Winam Gulf in Lake Victoria, and at Songhor, on the mainland, a
few miles north of Koru. Leakey, MacInnes, and other scientists continued to revisit Rusinga
Island and Songhor and opened new Miocene sites in western and northern Kenya during
the 1930s and 1940s (L. Leakey, 1937; M. Leakey, 1984; MacInnes, 1943). In 1948, a
University of California expedition recovered a few Miocene anthropoid fossils from the
Lothidok Hills in northern Kenya (Madden, 1980; M.G. Leakey et al., 1995).
2.1 Proconsul, Sivapithecus, and Limnopithecus
In 1951, Wilfrid LeGros Clark and Louis Leakey published a detailed monograph on the
226 anthropoid specimens that had been collected before September 1948, from Rusinga
Island, Maboko Island, Songhor, Koru and Lothidok. They consisted mostly of fragmentary lower and upper jaws and isolated teeth. Few of the upper and lower dentitions could
be associated with confidence as belonging to the same individual. A notable exception is
the skull of Proconsul heseloni, which was discovered in 1948 on Rusinga Island by Mary
Leakey. Postcranial remains were quite rare and generally fragmentary.
Clark and Leakey (1951) diagnosed four species of dentally great ape-like forms:
Sivapithecus africanus and small, medium and large species of Proconsul: Proconsul
africanus, Proconsul nyanzae, and Proconsul major, respectively. They further diagnosed
two species of dentally gibbon-like forms: Limnopithecus legetet and Limnopithecus
macinnesi. With Hopwood’s concurrence, they sank Xenopithecus into Proconsul africanus.
Clark and Leakey (1951) concluded that species of Limnopithecus belong to the
Hylobatidae, and though somewhat inclined to create a new subfamily for Proconsul spp.,
ultimately they left them in the Dryopithecinae of the Pongidae.
Clark and Leakey (1951) suggested that Propliopithecus gave rise to more advanced
hylobatine apes like Limnopithecus, and that Proconsul was derived from them.
Limnopithecus legetet and Limnopithecus macinnesi represented not greatly modified survivals of the ancestral stock from which Proconsul emerged. They considered Proconsul
to be a probable ancestor of modern African apes, but they did not designate which species
of Proconsul may have given rise to Pan and Gorilla. Limnopithecus legetet may have
been ancestral to Pliopithecus and ultimately, through Pliopithecus, to modern lesser apes.
They considered Sivapithecus africanus to be the most likely ancestor of the Eurasian
dryopithecine apes.
Clark and Leakey (1951) were not specific about possible ancestry of the Hominidae.
They proposed that specialization for brachiation occurred independently in the ancestral
Asian and African apes. In their scheme, hominid evolution did not include a brachiating
phase. Instead, there was a direct transformation of limbs like those of Proconsul because
of selection for bipedalism.
In 1948, Louis Leakey discovered associated jaws and limb bones of at least four
Limnopithecus macinnesi in a block of limestone on Rusinga Island. They were
monographed by Clark and Thomas in 1951 and were restudied by Denise Ferembach
(1958). Clark and Thomas (1951, p. 12) concluded that the posture and gait of
SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES
17
Limnopithecus probably “resembled the quadrupedal monkeys rather than the brachiating
gibbons.”
With the addition of two rib fragments, a badly damaged fragment of humeral shaft,
and a fragment of scapula, Ferembach (1958) concluded that Limnopithecus possessed no
special affinity with hylobatid apes. Instead, she inferred that Limnopithecus had closer
affinities with African pongid apes, especially chimpanzees. Further, she stated that filiation among Limnopithecus legetet, Pliopithecus antiquus, and Pan paniscus was supported
by available fossil evidence.
Ferembach (1958) concluded that Limnopithecus was basically arboreal since nearly
all of its postcranial characteristics resemble those of chimpanzees or colobine monkeys.
She inferred that Limnopithecus macinnesi progressed by arm-swinging, though not of a
modern hylobatid sort, and quadrupedism in trees; but they walked bipedally on the ground.
She provided no direct morphological evidence that Limnopithecus macinessi were bipedal. She simply surmised that they might have been bipedal because they lacked features
related to terrestrial quadrupedism and had a predisposition for brachiation.
In 1951, on Rusinga Island, T. Whitworth collected postcranial bones of a subadult
Proconsul, which were closely associated with upper and lower dentitions attributable to
Proconsul africanus. The specimens were monographed by Napier and Davis (1959),
who concluded that Proconsul africanus possessed many features that indicate arboreal
habits, including both quadrupedism and some brachiation, but there was no direct evidence for terrestrial habits.
Three decades later, Alan Walker (1992) extracted several additional postcranial bones
from a block of limestone that had been returned by the British Museum to the National
Museums of Kenya. They belonged to the same individual [KNM-RU 2036] that Whitworth
had discovered in 1951. Further search on Rusinga Island also produced an informative
leg and foot, lacking phalanges, which were reasonably assigned to Proconsul nyanzae
(Walker and Pickford 1983; Walker and Teaford 1988, 1989).
3. TAXONOMIC SHUFFLES, ANCESTORS, AND FUNCTIONAL INTERPRETATIONS: 1960–1999
The period of initial description and taxonomy of the African Miocene anthropoids (1926–
1959) was followed by taxonomic reassignments, somewhat more fine-grained functional
and phylogenic interpretations, and discoveries of additional specimens.
3.1 Limnopithecus, Pliopithecus, Dendropithecus, and Proconsul
In 1963, Elwyn Simons sank Limnopithecus into Pliopithecus, arguing that geographic
separation should not outweigh morphological similarity when considering possible congeneric status for primate species. Ten years later, Simons and Fleagle (1973, 140) withdrew this view, stating that “although the dentitions of the two forms are indeed very
similar, particularly in the lower molars, the skeletal evidence suggests that generic distinction is indeed justified. Although difficult to evaluate quantitatively, the postcranial
differences are certainly greater than those separating modern ape genera.” They concluded that Limnopithecus macinnesi was an arboreal arm-swinging form based on simi-
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larities of its forelimb with that of Ateles.
In 1977, Peter Andrews and Simons created a new genus for Limnopithecus macinessi,
largely because its limb bones evinced greater development of suspensory behavior than
those of other Miocene anthropoids. They renamed it Dendropithecus macinnesi. The
only postcranial features that they specifically mentioned in the diagnosis of Dendropithecus
are hind limb bones similar in size range to Hylobates; length and slenderness of the long
bones, which sets it apart from Pliopithecus and Dryopithecus, including Proconsul; lack
of conspicuous muscular markings; straightness of the humeral shaft; and the lack of the
entepicondylar foramen and broad distal humeral condyles of Pliopithecus.
In 1983, Fleagle proffered that, like Ateles, Dendropithecus macinnesi was a very
suspensory arboreal quadruped. Further, he concurred that Proconsul africanus was an
arboreal quadruped and less suspensory than Dendropithecus macinnesi or Pliopithecus.
On the other hand, on the basis of an allometric study of modern and Miocene anthropoids and their limb proportions, Aiello (1981) concluded that while Proconsul africanus
were below-branch feeders, Dendropithecus and Pliopithecus were above-branch feeders.
She further stated that Proconsul africanus was a more likely ancestral type for the extant
Pongidae and Homo than the other Miocene anthropoid species for which there was postcranial evidence.
Jungers (1984) conducted an extensive allometric analysis of the locomotor skeletons
of anthropoid primates, leading him to conclude that Dendropithecus and Pliopithecus had
long limbs and were basically arboreal, suspensory, monkey-like creatures rather like Ateles,
but without a prehensile tail. Also in contrast to Aiello (1981), Jungers (1984) concluded
that Proconsul africanus had relatively short limbs and was a relatively slow-moving arboreal quadruped. Here he echoed Walker and Pickford’s (1983) conclusions based on
more complete remains of KNM-RU 2036.
3.2 Proconsul, Dryopithecus, and Sivapithecus
In 1962 and 1963, Louis Leakey proposed the erection of a new family, the Proconsulidae,
which would include the genus Proconsul and some specimens of Dryopithecus and
Sivapithecus. He did not specify which individual fossils he would include in the new
family. He commented that erection of the Proconsulidae was justified by the distinctive
structure of the canine teeth, the face, and, where known, the skull. In particular, he cited
the shape of the mandibular arch, the nature of the mandibular fossa, the absence of a
simian shelf, and the special nature of the canine teeth (L. Leakey, 1963).
On the basis of a comprehensive review of available fossil materials, in 1965 Simons
and Pilbeam sustained Gregory and Hellman’s pongid subfamily, the Dryopithecinae, which
Leakey had termed a dust bin, and rejected Leakey’s proposal for the Proconsulidae. Indeed, they pursued a course that was diametrically opposite to that of Leakey and sank
Proconsul into Dryopithecus.
Simons and Pilbeam (1965) retained the nomen Proconsul as a subgenus of
Dryopithecus and sank Proconsul africanus, Proconsul nyanzae, and Proconsul major
into it. They arrived at this decision after systematically comparing Proconsul africanus
with the type specimens of Dryopithecus fontani. LeGros Clark, senior author of the
original expanded diagnosis of genus Proconsul, concurred with their revision.
Simons and Pilbeam (1965) confirmed the essential identity between the type maxillary fragment of Sivapithecus africanus and some maxillae attributed to Indian Sivapithecus,
SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES
19
especially Sivapithecus sivalensis. Further, they concluded that there was no justification
for generic distinction between Sivapithecus and Dryopithecus. Thus, they sank
Sivapithecus africanus into their newly created taxon, Dryopithecus (Sivapithecus)
sivalensis.
Simons and Pilbeam (1965) suggested that Dryopithecus nyanzae might be close to
the ancestry of Ramapithecus punjabicus and thus remotely related to later Hominidae.
They proposed that Dryopithecus major were almost certainly ancestors to modern gorillas. They inferred that either Dryopithecus fontani or Dryopithecus nyanzae were probably ancestors to modern chimpanzees.
3.3 Limnopithecus, Micropithecus, and Dendropithecus
In 1958, Walter Bishop recovered fragmentary mandibular and isolated dental specimens,
which Louis Leakey identified preliminarily as Limnopithecus legetet and Proconsul
nyanzae, respectively, on the flank of the Napak volcano in the Karamoja District of Uganda.
Further, in 1961, Bishop and Whyte (1962) collected additional large hominoid specimens
from Napak and from the vicinity of Moroto Mountain in the Karamoja District. Later in
1961, David Allbrook collected more remains of a large hominoid at Moroto II (Allbrook
and Bishop, 1963). During a 6-week period in 1963 and 1964, Bishop (1964) and company systematically collected many mammalian remains from Napak and Moroto, including a well-preserved palate and snout with face present to the lower left orbit of a small
species provisionally referred to Limnopithecus. Fleagle’s (1975) preliminary comments
on the palate from Napak IV were that the proportions of the maxillae, zygomatic bones
and teeth are much more similar to those of a living gibbon than those of Pliopithecus are,
and Simons and Fleagle (1973, p. 138) stated, “In morphology and facial proportions the
specimen is virtually identical to living gibbons. . .although it is considerably smaller in
absolute size.”
In 1969, Walker provisionally reported that specimens of Limnopithecus legetet were
among the fossils collected by Makerere University College expeditions, beginning in
1965, from the Bukwa II site, on Mount Elgon in the Sebei District of Uganda.
In 1978, Fleagle and Simons diagnosed a new species, Micropithecus clarki, on the
basis of dental and cranial bits from the Miocene deposits at Napak. They concluded that
it had greatest affinity with Dendropithecus macinnesi and that it had no clear link with
specific Oligocene anthropoids or with Pliopithecus of Europe.
Pickford (1982) noted that if Micropithecus or Dendropithecus incorporated
bilophodonty into their molars, they would be viable ancestors for Victoriapithecus, a Middle
Miocene monkey that is especially abundant on Maboko Island. If this scenario were
correct, the Cercopithecoidea evolved in Africa from small-bodied dental apes during the
Early Miocene. Six years later, Pickford and Senut (1988, p. 51) rejected the possibility
that a species of East African Early Miocene anthropoid could have evolved into
Victoriapithecus because of “the morphological distance between Victoriapithecus and all
lower Miocene primates from West Kenya.”
3.4 Proconsul, Dryopithecus, and Morotopithecus
At Moroto II, the 1963–64 expedition collected 56 additional pieces, which Bishop (1964)
ascribed to the same individuals of Proconsul major as the 1961 palatal and mandibular
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fragments. Allbrook and Bishop (1963) gave preliminary descriptions of the cranial remains. In 1968, Walker and Rose described remarkably African ape-like vertebral remains, presumably of one individual, from Moroto II.
The Ugandan remains of Proconsul constituted the primary empirical base for Pilbeam’s
(1969) doctoral thesis at Yale University. He was inclined to associate the palate, two
mandibular fragments and vertebral fragments from Moroto II as a single male of
Dryopithecus (Proconsul) major. He concluded that all of the large hominoid specimens
from the three Napak sites belong to Dryopithecus major. He described the face as a
scaled-down long-snouted male gorilla with a gracile upper face. From the relatively lowcrowned teeth, shallow palate, and other features, Pilbeam (1969) inferred that the Ugandan pongids were less well adapted than modern gorillas are to chewing tough vegetable
matter.
Pilbeam’s (1969) reassessment of Kenyan specimens of Proconsul and Sivapithecus
indicated close morphological affinities and conspecific status among Dryopithecus major
from Koru and Songhor and the large Ugandan hominoids. He concluded that Dryopithecus
nyanzae probably represents remnant populations of the ancestral stock that gave rise to
Dryopithecus major. Progressive adaptation to a tough vegetal diet on the heavily forested
slopes of active volcanoes like Moroto and Napak transformed Dryopithecus major into
Gorilla gorilla. Pilbeam’s (1969) Dryopithecus major might well have been a knucklewalker, though probably it was more active and less terrestrial than extant gorillas are.
Pilbeam (1969) concluded that Dryopithecus africanus, though probably lacking
knuckle-walking adaptations, was a likely ancestor to Pan troglodytes. This would mean
that the lineages leading to modern chimpanzees and gorillas were specifically separated ≥
20 Ma.
Pilbeam (1969) retreated from the assignment of certain medium-sized African specimens to Dryopithecus sivalensis (Simons and Pilbeam 1965) on the grounds that they
were probably earlier than the Indian forms, though he thought they might represent ancestors of Eurasian Dryopithecus, especially Dryopithecus (Sivapithecus) sivalensis.
In 1994 and 1995, Gebo and coworkers (1997) collected additional postcranial specimens from Moroto I and II. Although dated at 20.6 Ma, they evidence more ape-like
features than any other Early or Middle Miocene anthropoid. Gebo et al. (1997) created a
new species, Morotopithecus bishopi, for the entire collection of large anthropoid specimens from Moroto. Unfortunately, they may have included a nonprimate scapular fragment (MUZM 60) in the hypodigm (Benefit, 1999; Pickford et al., 1999; Senut, 1999).
Further, Gommery (2003) noted that there are two large hominoids represented at Moroto:
Ugandapithecus major (formerly Proconsul major) and Afropithecus turkanensis, of which
Morotopithecus is a synonym.
3.5 Fort Ternan
In 1961, Louis and Mary Leakey directed the collection of > 1200 fossils at Fort Ternan,
which is a few miles south of Koru. In 1962, Louis Leakey announced the discovery of
primates there but concentrated on specimens that he diagnosed as Kenyapithecus wickeri.
He mentioned discovery of “a very large upper canine, scarely [sic] distinguishable from
those of Proconsul nyanzae. . .” (L. Leakey, 1962, p. 690).
In 1968, Leakey gave a brief report in Nature on the primates that were associated
with Kenyapithecus wickeri. He also mentioned isolated teeth and parts of two mandibles
SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES
21
of Hylobatidae that were too different to be assigned to Limnopithecus legetet or
Limnopithecus macinnesi. He noted that there were > 300 specimens of Miocene
Hylobatidae at the Nairobi Museum.
In a commentary in Nature, Simons (1969) accepted the hylobatid status of the Fort
Ternan specimens but referred them to Pliopithecus because at the time he considered
Limnopithecus to be a junior synonym of Pliopithecus.
One mandibular specimen of a nonhylobatid primate from Fort Ternan evidenced a
simian shelf and bicuspid P3, features that Leakey (1968) had never observed in specimens
of Proconsul, but which occur in European and Asian Dryopithecus. Therefore, he provisionally referred this new Fort Ternan specimen to Dryopithecus. Leakey (1968) also
noted that there were two canine teeth typical of Proconsul in the collection.
Simons (1969) concurred that the new mandible from Fort Ternan was that of
Dryopithecus and referred it to Dryopithecus cf. sivalensis. But he suggested that the
canines should also be referred to Dryopithecus sivalensis because canines of Indian
Dryopithecus sivalensis closely resemble those of Dryopithecus nyanzae, and it is unlikely that Dryopithecus nyanzae survived as lately into the Miocene.
Andrews and Walker (1976) concluded that, apart from Ramapithecus, there are 3
hominoid species from the Fort Ternan deposits. Limnopithecus legetet was the most
common primate at the site. Fourteen specimens and probably many fewer individuals
represented it. They concluded that Dryopithecus cf. nyanzae was represented at Fort
Ternan by 7 specimens. They provisionally recognized Proconsul cf. africanus on the
basis of ≥ 2 isolated teeth.
In 1986, Pickford listed Micropithecus sp., Rangwapithecus gordoni, Kenyapithecus
wickeri, perhaps Proconsul sp., and an oreopithecoid at Fort Ternan. In 1992, Harrison
confirmed the presence of Kenyapithecus wickeri and Proconsul sp. and identified specimens of Simiolus sp., probably Oreopithecus sp., and perhaps Kalepithecus sp. in the Fort
Ternan anthropoid sample.
3.6 Taxonomic trials of the 1970s
During the 1950s, 1960s, and sporadically thereafter, collecting continued at established
eastern African Miocene localities and further primate remains were recovered from Rusinga
Island, Songhor, Koru, and Maboko Island. Anthropoid fossils also were found on Mfangano
Island in the Winam Gulf of Lake Victoria. Andrews (1978) noted that the size of the
fossil primate collection at the Centre for Prehistory and Palaeontology in Nairobi had
more than doubled between 1951 and 1970.
In 1978, Andrews listed the following numbers of specimens:
Species
n
Pickford (1986)
Dendropithecus macinnesi
160
152
Proconsul (Rangwapithecus) gordoni
79
78
Proconsul (Rangwapithecus) vancouveringi
10
5
Limnopithecus legetet
136
159
Proconsul africanus
120
146
Proconsul nyanzae
109
104
Proconsul major
81
75
Pongidae indet.
5
16
TOTAL
700
735
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R. H. TUTTLE
To Andrews’ (1978) total should be added the ≥ 20 specimens of Micropithecus clarki,
which he provisionally recognized as Limnopithecus legetet. In 1981, Harrison (p. 133)
noted 78 specimens that might be Micropithecus from Koru, but Pickford (1986) listed
only one specimen of Micropithecus clarki at Koru, with the bulk of specimens being from
Chamtwara (n = 49) and Legetet (n = 14), in the Koru area, and Napak (n = 13), Uganda.
In 1970, Andrews drew some novel inferences about pongid phylogeny on the basis of
2 previously undescribed specimens from Kenya. He concluded that a mandibular fragment
[KNM-RU 900], which was discovered in 1956 on Rusinga Island, should be referred to
Aegyptopithecus. He concluded that Aegyptopithecus zeuxis, his new Aegyptopithecus
sp., and Limnopithecus legetet belonged to the same phylogenic lineage. In 1978, he sank
his Aegyptopithecus sp. in the hypodigm of Dendropithecus macinnesi.
Andrews (1979) proposed that a reasonably complete palate containing all teeth except
the incisors, from Songhor [KNM-SO 700], should be referred to Proconsul sp. indet. and
that it probably represented ancestral Pongo. The tips of its canines are broken off; Andrews
(1979) surmised that they had not fully erupted. He noted that, both in size and morphology,
its closest affinities were with Proconsul africanus.
As part of a major taxonomic reshuffling and preliminary accommodation of the newer
specimens from Kenyan Miocene localities, Andrews transferred Limnopithecus legetet
from the Hylobatidae into the Dryopithecinae, but he left Limnopithecus macinnesi in the
Hylobatidae. He continued to recognize the three species of Dryopithecus (Proconsul),
viz. D. (P.) africanus, D. (P.) nyanzae, and D. (P.) major, and proposed two new species:
Dryopithecus gordoni and Dryopithecus vancouveringi, in a new subgenus Rangwapithecus.
The holotype of Dryopithecus (Rangwapithecus) gordoni is the Songhor-700 palate
(Andrews, 1974), which Andrews (1970) previously had referred to Proconsul sp. indet.
The hypodigm consisted of 79 specimens, mostly from Songhor, but there were also
purported specimens from Rusinga and Mfangano Islands. Some specimens in the
hypodigm were undescribed, while others had been assigned to Limnopithecus macinnesi,
Proconsul africanus, and P. nyanzae.
In 1974, the hypodigm of Dryopithecus (Rangwapithecus) vancouveringi consisted
of 7 specimens, including only the upper postcanine dentition and parts of the maxilla
(Andrews, 1974). It is distinguished from D. (R.) gordoni chiefly in its somewhat smaller
size. Judith and John Van Couvering found the type specimen [KNM-RU 2058] on Rusinga
Island in 1968. It purportedly occurred also on Mfangano Island and perhaps also on
Maboko Island (Andrews, 1978). Pickford (1986) listed only 5 specimens total from Hiwegi
and Songhor.
Andrews ended his brief 1974 report with the following pessimistic comment: “In my
opinion it is no longer feasible to suggest direct ancestral-descendent relationships between
fossil and living species. Presumably one or more of the Miocene species was ancestral to
the later pongids, but which this was, and whether one or more species was also ancestral
to the Eurasian dryopithecines, can not be known from the available evidence (p. 190).”
Apparently, this sober thought did not deter him (Andrews, 1978, p. 210), his
contemporaries, his students and other successors from proffering speculative phylogenic
models, which are now arrogantly termed “phylogeny (or phylogenetic) reconstructions.”
In a 1978 monograph based on his doctoral thesis, Andrews reiterated that
Dendropithecus macinnesi belonged in the Hylobatidae, and he placed 6 species of African
SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES
23
Miocene Hominoidea in the Dryopithecinae of the Pongidae: Limnopithecus legetet,
Proconsul (Proconsul) africanus, Proconsul (Proconsul) nyanzae, Proconsul (Proconsul)
major, Proconsul (Rangwapithecus) gordoni, and Proconsul (Rangwapithecus)
vancouveringi.
Although Andrews (1978) endeavored to find clear-cut morphological features that
separate these species, most of them are differentiated on the basis of relative size (and
perhaps also by site). Andrews (1978) sank Sivapithecus africanus into Proconsul nyanzae,
stating that they may well be ancestors to later Sivapithecus sivalensis. He agreed with
Pilbeam (1969) that Leakey’s specimens of Kenyapithecus africanus could be referred to
Proconsul nyanzae or Proconsul major.
3.7 Taxonomic trials of the 1980s and 1990s
The trend toward splitting, resurrecting taxa, and naming new ones accelerated during the
1980s and 1990s. Pickford’s 1986 compilation is a prime example. He listed no fewer
than 15 African Miocene anthropoid species binomially and noted 8 more that awaited full
and formal nomination. He raised Rangwapithecus and the newly revived Xenopithecus
from subgeneric to generic rank, resurrected Kenyapithecus, and accepted several new
species, including Mabokopithecus clarki, Micropithecus songhorensis, and Limnopithecus
evansi. Concurrently, Harrison (1986a, 1989) added a new species, Nyanzapithecus
pickfordi, and changed Proconsul (Rangwapithecus) vancouveringi to Nyanzapithecus
vancouveringorum. Harrison (1986b) proposed that Nyanzapithecus is an earlier Miocene
ancestor for the Late Miocene European oddball, Oreopithecus bambolii. Harrison (1986a)
sustained Rangwapithecus gordoni, which might approach the Early Miocene ancestor of
Nyanzapithecus.
In 1993, Walker and coworkers named a new species, Proconsul heseloni, for the
smaller specimens of Proconsul from Rusinga and Mfangano, but retained the nomen
Proconsul africanus for specimens from Koru and Songhor.
Harrison (1988) also implemented a major taxonomic revision of the smaller Early
Miocene catarrhine primates from western Kenya and Uganda. He not only sustained
Dendropithecus macinnesi, Micropithecus clarki, and Limnopithecus legetet but also
recognized Limnopithecus evansi and a new species, Kalepithecus songhorensis (formerly
Micropithecus songhorensis), which is represented at Koru and Songhor. Moreover,
Harrison (1988) referred some Middle Miocene specimens from Moboko Island to a new
species, Micropithecus leakeyorum, but Benefit (1991) sank them in Simiolus.
Having yielded several thousand primate specimens, Maboko is one richest
paleoprimatological sites in East Africa. It is the type-site of Kenyapithecus africanus,
Mabokopithecus clarki, Nyanzapithecus pickfordi, and Victoriapithecus macinnesi. During
a 6-week excavation in 1997, Gitau and coworkers (1998) recovered 22 specimens of
Kenyapithecus africanus, 45 each of Mabokopithecus clarki and Nyanzapithecus pickfordi,
17 of Simiolus leakeyorum, and 327 of Victoriapithecus macinnesi. Based on postcranial
specimens, McCrossin and Benefit (1994) concluded that Kenyapithecus africanus was
adapted to terrestrial pronograde digitigrade quadrupedal locomotion, which set them apart
from other Miocene species.
In 1998, Benefit and coworkers concluded that Mabokopithecus clarki is at least
congeneric, and perhaps conspecific, with Nyanzapithecus pickfordi. Accordingly,
Nyanzapithecus pickfordi becomes Mabokopithecus pickfordi (or M. clarki, if conspecific
24
R. H. TUTTLE
with M. pickfordi) and Nachola Nyanzapithecus harrisoni becomes Mabokopithecus
harrisoni.
In northern Kenya, Kalodirr is the 16–18Ma type site of Afropithecus turkanensis,
Turkanapithecus kalakolensis, and Simiolus enjiessi (R. Leakey and M.G. Leakey, 1986a,b;
R. Leakey et al., 1987; R. Leakey et al., 1988a,b; Boschetto et al., 1992). The former two
species are cranially among the best-known Miocene anthropoids. Postcranial features of
Afropithecus and Turkanapithecus appear to be logical precursors for those in later ape
skeletons, though they lack special features related to obligate suspensory feeding and
knuckle-walking (Rose, 1993). Afropithecus turkanensis was probably also present at
Buluk in northern Kenya (R. Leakey and Walker, 1985; McDougall and Watkins, 1985).
Two sites—Nachola and Namurungule—in the Samburu Hills, south of Lake Turkana,
have provided intriguing hominoid specimens due to the efforts of the 1980 and subsequent
Japan/Kenya Expeditions (Ishida, 1984).
Primate remains (n > 200) are common components of the Nachola fauna (Sawada et
al., 1998). Pickford (1986) proposed that Kenyapithecus cf. africanus, Micropithecus sp.,
and perhaps Xenopithecus sp. are represented in the 15–14Ma Nachola collection. However,
Kunimatsu (1997) and Sawada et al. (1998) noted that the Nachola anthropoids are
Nyanzapithecus harrisoni, Kenyapithecus sp., and Victoriapithecus. Postcranial remains
indicated that Nachola Kenyapithecus were accomplished arboreal quadrupeds and climbers
that engaged in little suspensory behavior (Rose et al., 1996; Nakatsukasa et al., 1996,
1998).
Expanded samples of dentognathic (Kunimatsu et al., 1999) and postcranial
(Nakatsukasa et al., 1999) remains of the Nachola large hominoid cast doubt on its being a
species of Kenyapithecus. Accordingly, Ishida et al. (1999) named a new species:
Nacholapithecus kerioi.
Based on a partial skeleton from Kipsaramon, Tugen Hills, north-central Kenya, Ward
et al. (1999) erected a new species, Equatorius africanus, into which they sank Kenyaithecus
sp. from the Aiteputh and Nachola Formations at Nachola and from the Muruyur Formation,
Tugen Hills and all specimens of Kenyapithecus africanus from the Maboko Formation of
Maboko Island, Majiwa, Kaloma, Nyakach, and Ombo.
The Namurungule Formation contains one of the precious few Late Miocene sites in
eastern Africa (Sawada et al., 1998). The single hominoid specimen [KNM-SH-8531] is a
left maxilla with P3–M3, which Ishida and Pickford (1997) named Samburupithecus
kiptalami. It is ≈ 9.5 Ma, which makes it the most complete hominoid mandibular specimen
from early Late Miocene eastern Africa. Pickford and Ishida (1998) concluded that dentally
it is closest to early Hominidae, viz. Praeanthropous africanus (Australopithecus afarensis
and A. anamensis).
The Ngorora Formation, in the Baringo Basin, Kenya, which spans a > 2 million year
period between 13 and < 10 Ma, yielded 11 primate specimens. In addition to cercopithecoid
monkeys, 8 specimens were provisionally assigned to Kenyapithecus, Proconsul, and a
small ape (Hill et al., 1985; Hill and Ward, 1988; Hill, 1994).
3.8 Return of the Proconsulidae
In 1982 (p. 18), Pickford echoed Louis Leakey (1962, 1963) in noting that Proconsul and
other unspecified African Early Miocene large genera of Catarrhini probably do not belong
SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES
25
in the Pongidae. Harrison (1987) and others resurrected Leakey’s (1963) once disregarded
family, the Proconsulidae, to accommodate many African Miocene species. For example,
in 1988 Fleagle placed Dendropithecus, Limnopithecus, Micropithecus, Proconsul,
Rangwapithecus, and Simiolus, together with two Chinese Miocene species
(Dionysopithecus and “Platydontopithecus”) in the Proconsulidae. He accepted
Nyanzapithecus as a member of the Oreopithecidae and left Afropithecus, Kenyapithecus,
and Turkanapithecus in Family incertae sedis of the Hominoidea. This resembles de Bonis’
(1987) scheme, except that de Bonis placed Rangwapithecus in the Oreopithecidae and
Turkanapithecus in the Proconsulidae and did not classify Dendropithecus familially.
4. CONCLUSIONS
All in all, despite periodic taxonomic shuffles of specimens, the Miocene dental apes of
eastern Africa represent a remarkable adaptive radiation of forest, dense woodland, and
perhaps more open habitat species, which has been compared with the radiation of the
Cercopithecoidea. The three modern African apes—Gorilla gorilla, Pan troglodytes, and
Pan paniscus—are an impoverished faunal component in comparison with their African
Miocene cousins and cercopithecoid contemporaries. Premature attempts to link specific
African Miocene apes to extant African apes, e.g. Proconsul africanus to Pan troglodytes
and Proconsul major to Pan gorilla, have been discredited. Indeed, it is difficult even to
derive a species of Eurasian Middle Miocene apes directly from the eastern African Miocene
species, though it is generally thought that the latter must have evolved from African
precursors.
The problem of linking Early and Middle Miocene anthropoids to Pan, Gorilla, and
Homo is particularly exacerbated by the poor fossil record of apes during the Late Miocene
and Pliocene of Africa. The only informative specimen representing the morphology of a
Late Miocene African ape is the maxilla of Samburupithecus kiptalami. This has stimulated
researchers to look to Europe for proximate Miocene ancestors of African apes and
australopiths (de Bonis, 1987; Andrews et al., 1996; Begun and Kordos, 1997; Begun et
al., 1997).
5. ACKNOWLEDGEMENTS
I thank Dr. Hidemi Ishida for inviting me to the benchmark symposium in 1999, for which
I prepared an earlier version of this paper, and for his gracious hospitality and that of our
other hosts and assistants, especially Dr. Masato Nakatsukasa, who faithfully directed me
to the right dining room, vehicle, kinen-shashin, and costume.
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